Sportswear such as mountain climbing wear is generally required to have mobility or lightness upon wearing, as well as excellent moisture permeability, waterproofing property and the like. Moisture permeability is an important property for suppressing the unpleasant feeling due to, for example, the sultriness caused by moisture generated from the body, such as sweat, staying within the clothes.
The moisture permeability of clothes as described above is known to be able to be improved by using a moisture-permeable film as one of the materials used to produce clothes. A known example of such moisture-permeable films is a porous moisture-permeable film (see, for example, Patent Document 1).
However, there are many cases in which such moisture-permeable films are produced by coating a resin composition dissolved or dispersed in a solvent such as an organic solvent or water on a releasable film followed by removing the solvent, and in the case of such methods, there have been problems such as an increased burden on the environment attributable to volatilization of the organic solvent, and increased energy consumption as a result of having to remove the solvent.
The aforementioned problem attributable to the solvent is known to be able to be solved by using a hot melt resin composition that is substantially free of solvent, and a known example of such a hot melt resin composition is a moisture-curable polyurethane hot melt composition (see, for example, Patent Document 2).
However, films obtained by using conventionally known moisture-curable polyurethane hot melt resin compositions did not have a level of moisture permeability adequate for practical use, while also not satisfying requirements relating to flexibility (pliable texture) or mechanical strength that permitted use in the production of clothes and the like. In addition, since these films swelled when contacted with water and the like causing a considerable decrease in film strength, there were cases in which it was typically difficult to use such films in materials such as clothes that was subjected to laundering and the like.
In this manner, conventional moisture-curable polyurethane hot melt resin compositions presented difficulties in obtaining moisture-permeable films that provided adequate levels of moisture permeability, flexibility and mechanical strength for practical use while also demonstrating superior waterproofing property.
However, when producing a moisture-permeable film using a moisture-curable polyurethane hot melt resin composition as described above, there are many cases in which it is necessary to wind the moisture-curable polyurethane hot melt resin composition onto roller while coated onto a releasable film in a heated molten state, and then allowing curing to proceed adequately by allowing to stand for a fixed period of time.
However, since there are many cases in which winding onto a roller as described above is carried out before the moisture-curable polyurethane hot melt resin composition has completely cured, in cases in which separation of the moisture-permeable film composed of the moisture-curable polyurethane hot melt resin composition from the back of the releasable film in contact therewith is poor when the composition is unwound, roughening occurs on the surface of the moisture-permeable film during separation, thereby resulting in the problem of a decrease in the surface quality thereof.
As has been described above, there has yet to be disclosed a moisture-permeable film which has superior moisture permeability, flexibility (pliable texture), mechanical strength and waterproofing property at levels enabling the use thereof in the production of textile products such as clothes, which is not susceptible to the occurrence of a decrease in surface quality caused by roughening, and which does not cause an increase in the burden on the environment.                Patent Document 1: Japanese Unexamined Patent Application, First Publication No. 2002-327310        Patent Document 2: Japanese Unexamined Patent Application, First Publication No. 2007-63510        